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Hello, I just noticed my T. Peruvianus is developing a few purple areas mainly on the new growth from last summer. And I see this funky black stuff! What is happing and what can I do?? I did just water last week, it has been a while. It's been indoors here in Utah and ready for the outdoors about right now.

Thanks in Advance guys !!!

Hate to say it, but I think this calls for surgery. You need to cut it well clear of any discoloration.

greenknight wrote: ↑Sat Mar 05, 2022 9:48 am Hate to say it, but I think this calls for surgery. You need to cut it well clear of any discoloration.

Cleaning the knife very well between cuts.

Thanks for the reply people! Oh No, poor thing! What caused this and Is there a name for it? It seems to be happening on 3 of the 4 new growth from the bottom.

I've never had to cut a cacti before, that really sucks. So there's no way she'll recover from this on her own?? If not should I just cut off the WHOLE growth from the main cacti? Thanks, again!

No, it won't recover by itself. Don't wait too long. As previously mentioned, clean your knife thoroughly after each cut. You can also apply aluminum powder or reticulated sulphur to the cut to prevent infection.
What do you mean by "the WHOLE growth"?
As for the main stem, cut away as much as needed. Meaning, no discoloration should be present in the tissue after the cut. If necessary, make a second or third cut.
As for the offsets, I don't know. They are also discoloured? Maybe remove them entirely? Another opinion would be good.

Based on the first picture given, one of the offsets also looks discolored. So surgery will be needed on any of the offsets that are discolored.

Sorry guys my bad. The Main cactus seems fine. The offsets (now I know what they're called) have the issues. There are 4 offsets. The diseased pics are of 2 offsets. 1 is the worst in the pics. 2 others are showing slight signs of purple with black goop and 1 seems fine, for now. So would it be best to remove the 4 offsets all together? Thanks for your info and help!

I suggest you simply get rid of the discolored areas. If the areas continue to spread, then, and only then, would I remove the offsets.

Ok, thank you so much! Sine I'm new to surgery forgive my lack of knowhow. If 1 'rib' is purple between 2 green ribs, do I cut into the adjacent green ribs?
AND...
If 3 (or more) ribs are purple at the top would you suggest cutting the whole top of the offset off about an inch down?? Forgive my stupid question if it is indeed one.

Just get rid of any discolored material and tissue. If the other surrounding areas are healthy, there's no need to do surgery on them.

Another idea.
It might just be edema from overwatering because you mentioned you just watered it and it looks very plump. The Black ooze is alkoloids.

I have had same issues, it usually scars the damage but it can also be fatal because there is an opening for bacteria. See picture from my cactus damage from last year the cactus is fine just ugly.

My Suggestion is to repot in more gritty soil and cut back on the watering.

In my opinion jheaton's cactus did suffer from rot and not oedema. I also think the black spot on your cactus is something else, but I could be wrong. I've had oedema on an opuntia and it looks entirely different from the rot jheaton is experiencing. In my case it looked a lot like a white hardened blister. It also didn't occur at the top of the plant, rather on the sides of the stems. I wonder how jheaton's plant is doing now...

Ohugal
I also had Edema on a large Echinocactus grusonii and it also looked like hardened blister afterwards. But I do belevie Edema look different on Peruvianus because of the Alkoloids that forms the black ooze. I also have same spots occuring on top spot of Peruvianus, i will post picture tomorow.

And as i said it might easily become infected if there is an opening but the main cause is overwatering.

ohugal wrote: ↑Sun Mar 27, 2022 9:20 am I wonder how jheaton's plant is doing now...

Thank you for your rely. All of the 4 offsets ended up like that. I cut out some here and there and ultimately hacked the top off of all 4 offsets. It would have been nice to have those but as long as the main guy is fine it's aok. Seems to be. Thanks again!

Ah good to hear it’s doing ok. Did you check the roots?